1. Field of the Invention
This invention relates to the strapping of bulk boxes, and more particularly, to a machine for the automated strapping of bulk boxes.
2. Prior Art
Containers have been developed in the prior art for the bulk storage and shipment of a variety of materials, including meat products, agricultural produce, flowable goods, and other consumer and industrial products. These containers are commonly referred to as bulk bins or bulk boxes, typically varying in size from forty to sixty inches deep and thirty to forty inches wide, and capable of holding and supporting in excess of four thousand pounds of goods.
Bulk boxes are made of various materials, but commonly employ corrugated cardboard in their construction. Liners are sometimes used to improve the strength of the boxes and to insure leakproof containment of the goods held therein.
The internal contents of these boxes, often fluid, provide minimal support of their own weight and rely upon the structural integrity of the container to support the full weight of the contents. Bulk boxes, unlike most corrugated containers, must resist strong forces in both horizontal and vertical directions. These conditions can cause the sidewalls to bulge outwardly and possibly fail. To alleviate this problem, one or more, typically four to eight, external reinforcing bands or straps of plastic or metal are sometimes applied to the boxes.
In the prior art, the reinforcing straps are manually applied to the boxes, generally with the boxes in a knocked-down or flattened state. This process is time-consuming and expensive, with the ratio of the cost of labor to the cost of materials often as much as 4:1.
Machines are known in the prior art for applying strapping around objects, including boxes, for bundling them together. The heaviest, or largest, strapping that can be handled with these machines is four hundred pounds. Reinforcing strapping as used in the present invention is typically six hundred pound strapping. Applicant is not aware of any prior art machine that applies reinforcing strapping to a container, or any bundling strapper that is capable of handling strapping larger than four hundred pounds.
Accordingly, there is need for an economical system and method for applying external reinforcing straps to bulk boxes.
In accordance with the invention, an automated system and method are provided for economically applying reinforcing straps to bulk containers.
With other costs remaining constant, the system and method of the invention enables external reinforcing straps to be applied to bulk boxes at a ratio of the cost of labor to the cost of materials of about 1:3, or a 12:1 improvement over the prior art.
The invention comprises an automatic strapping machine that applies one or more straps externally to a bulk box to reinforce the box. More specifically, the strapping machine of the invention applies a plurality of reinforcing straps around the outside of the box in spaced apart relationship along the length or height of the box, while the box is in its knocked-down or flattened condition. The straps can be uniformly spaced apart, or the straps nearer the bottom of the box can be spaced more closely together than the straps toward the top of the box, depending upon the requirements of a particular application. From four to eight straps are generally applied to a box, although this number can vary as desired or required.
The strapping machine of the invention has a plurality of strapping stations or stages through which the box, in a knocked-down or flattened state, passes for sequential application of the straps to different locations on the box. The straps are applied by strapping head assemblies positioned at the strapping stations, each of which receives a length of strapping material from a supply reel, encircles the box with a strap, secures the strap in encircling relationship to the box, and cuts the strap encircling the box from the length of supply strapping in preparation for continued movement of the box to the next station. Suitable sensing means, such as photocells or microswitches and the like, are positioned at each station to sense the position of the box and stop it in a predetermined location for application of the straps.
Each station may be constructed as a separate module having two strapping head assemblies. A single disconnectable data and power connection is provided. Each module will be large enough to hold an entire bulk box in process. All of the modules can be identical and interchangeable with one another, but the last module in a series preferably comprises a recovery module to apply any straps that were missed in an earlier station.
Further, the modules can operate independently of one another. That is, inoperability of one module, or one or more strapping heads at a module, will not affect the operation of another, except that a recovery module can apply any missing straps. This enables one or more strapping heads or modules to be taken out of service and the machine can still operate. Straps that would have been applied by the inoperable strapping head are applied by the recovery module, which can apply all of the straps if all of the preceding heads are inoperable.
In a preferred embodiment, two strapping head assemblies are provided at each station, with each head assembly arranged to position a strap at a predetermined location on the box. The head assemblies at subsequent stations are positioned to apply further straps at different predetermined locations on the box. A last station that normally is not utilized may be provided to apply a strap or straps that were inadvertently not applied at a preceding station.
An infeed can be provided to supply boxes to the machine to be strapped, or boxes can be hand fed to the machine. A stacker preferably is positioned to receive strapped boxes from the machine. As a box is called into the machine, any boxes in the system all shift one module toward the outlet. After module 1 has called for a box and all boxes have shifted downstream into place, all strapping head assemblies will activate. For a four station machine, with the fourth station serving as a recovery module, there will be six boxes in process at any given time. Each module will have a box ready for strapping, one box will be in the infeed ready for the next start cycle, and one box will be in the stacker. Each module, except the fourth in this example, will apply two straps on the box. The recovery (fourth) module will apply any missing straps. The cycle time for each strapping station is about 6.4 seconds, and approximately 545 boxes per hour can be strapped.
The placement of positioning of the straps, and initiation of operation of the strapping heads at each module, are controlled by sensors that detect the position of each box at a station and operate to cause a limit stop to move into the path of the box to halt its movement through the station at a predetermined position for placement of the straps applied at that station in specific locations on the box. After the straps have been applied, the limit stop is moved out of the way of the box and it is moved to the next station where another sensor and limit stop operate to position the box for placement of an further pair of straps at predetermined different locations on the box. This process is repeated at each station until all straps have been applied.
Control means senses when a strap or straps have been missed, and operates to cause the box to be stopped at one or more positions in the recovery station for application of the missing strap or straps.
In a specific example of the machine, the strapping heads in the strapping head assemblies are based on the EAM Mosca KSR bundle strapper, which is capable of threading, cutting and welding a six hundred pound strap. These heads have been modified in the present invention to increase the throat size to accommodate an eighty-four inch throat.